June 15, 2014

2012 was SDR year. some guys (Antti Palosaari and Eric Fry first) discovered possibility of using realtek RTL2832 based devices as generic radio.usually that chips can be found in usb dvb-t sticks which can bought with 10$ from most markets. In same year, i read an article on hackaday and decided to purchase one of them. and did almost all available stunts from positioning ships & airplanes to gathering weather data from satellites in past two years.

i was seen strange signals while playing with it, now compiled all of them in this article. my setup is 1x Terratec Cinergy T Stick, 1x indoor tv antenna with built-in amplifier and 1.6ghz netbook which is seen in picture. all signals recorded in same session at 14.06.2014

Signal #1: 415.6mhz Its looking like aprs stream, also frequency fits but no any decoders can handle that in my software arsenal.Signal #2: 448.5mhz that one is very similar to tty teletype, probably customized and encrypted for military purposes. also local police and fire department still uses old analog walkie-talkie systems in here, conversation stream can be seen in 450~455mhz.

Signal #3: 150.3mhz I have no idea about that, usually amateur satellites uses that frequency range but my setup cannot catch that signal in this level. it's a mystery.

Signal #4: 152.6mhz another signal in same frequency range, its like a telemetry data and most interesting one ever seen. due to signal level, probably its coming from a meteorology station where is 6km away from here.

edit on 30.06.2014: it was a network beacon of new model DMR radio. next week i monitored same channel about 48hrs and got a digital voice stream. decoded it via dsd+ and just hear conversation from new hospital of city.

Signal #5: 135~137mhz yes, most strange part is in here. i was seen that few times but i supposed its a device glitch or software error. then someday tried with different antennas & different angles and i seen signal level was changed. it's obvious to coming from far away and it's not human made. i seen some guy's article which is mentioning about detecting galactic rotation with software defined radio. he was demonstrating similar signal shapes in screenshots. my best guess is that's a frequency reflection from moon or other planet's surface. we're living in a huge signal ocean, that's possible.

playing with sdr is fun but it uses too much system resources, my opinion it cannot be used in business or other proffessional purposes. if interested, you can proceed following links to dive into ham-radio world: